"To address this question, one must look at differences and similarities between CALGreen and LEED in areas such as site characteristics, energy efficiency, water reduction, materials, and the indoor environment. When comparing individual areas within each standard, it’s important to recognize that LEED is a voluntary point-based rating system with four levels of certification. CALGreen, on the other hand, is a mandatory green building code that also includes optional “tiers” for projects seeking to go beyond the minimum level required.

Both CALGreen and LEED address five main categories relating to new commercial buildings: site, water, energy, materials and the indoor environment. Since LEED is a point-based rating system in which projects must achieve at least 40 of 110 possible points, it allows for flexibility and has few mandatory prerequisites. In contrast, all of the measures within CalGreen are mandatory, with the exception of the optional tiers."